Refining of sweet crude resources requires less capital input and less cost expenditure than processing heavy sour crudes. However, the processing of heavy sour crude has become an increasingly important option to meet the world's demand for hydrocarbon-based fuels. Heavy sour crude may be derived from bitumen. Bitumen is a form of petroleum that exists in the semi-solid or solid phase in natural deposits. Bitumen is a thick, sticky form of crude oil, having a viscosity greater than 10,000 centipoises under reservoir conditions, an API gravity of less than 10° API and typically contains over 15 wt % C5-asphaltenes.
Most, if not all, commercial upgraders for processing heavy crude have been built to convert heavy viscous hydrocarbons into crude products that range from light sweet to medium sour blends. Heavy oil upgraders basically achieve this conversion by using high intensity conversion processes. These processes may release up to 20% by weight of the feedstock as a coke byproduct and another 5% as off-gas product. Alternatively, these processes require significant hydro-processing such as ebullated bed hydrocracking and fixed bed hydro-treating to maximize the conversion of the heavy components in the feedstock to lighter, lower sulfur liquid products.
Various processes have been used to convert and/or condition oil sands bitumen into pipeline transportable and refinery acceptable crude. Of note, thermal cracking, catalytic cracking, solvent deasphalting and various combinations thereof (for example, visbreaking and solvent deasphalting) have been proposed to convert bitumen to hydrocarbon streams having characteristics suitable for pipeline transport and use as a refinery feedstock. Some examples of these methodologies are presented below.
In U.S. Pat. No. 4,454,023 (“the '023 patent”), a process for the treatment of heavy viscous hydrocarbon oil is disclosed. The process involves the steps of: visbreaking the oil; fractionating the visbroken oil; solvent deasphalting the non-distilled portion of the visbroken oil in a two-stage deasphalting process to produce separate asphaltene, resin, and deasphalted oil fractions; mixing the deasphalted oil (“DAO”) with the visbroken distillates; and recycling and combining resins from the deasphalting step with the initial feedstock. While the '023 patent provides a means for upgrading lighter hydrocarbons (API gravity>15), the API of a typical composition of Canadian bitumen is lower than this. In addition, thermal cracking will generally result in over-cracking and coking of the hydrocarbon stream. There is added complexity and cost associated with the two-stage solvent deasphalting system (e.g. separation of the resin fraction from the deasphalted oil, and recycling of the resin stream).
U.S. Pat. No. 4,191,636 describes a process in which heavy oil is continuously converted into asphaltenes and metal-free oil. The process involves hydrotreating the heavy oil to crack asphaltenes selectively and remove heavy metals such as nickel and vanadium simultaneously. The liquid products are separated into a light fraction and a heavy fraction of an asphaltene- and heavy metal-containing oil. The light fraction is recovered as a product and the heavy fraction is recycled to the hydrotreating step. It is not clear whether this process would be effective for the catalytic conversion of Canadian bitumen (API gravity<10).
Accordingly, there is an on-going need to develop cost-effective and efficient ways to process heavy hydrocarbons such as Canadian bitumen.
While there have been various processes disclosed for separating and treatment of a hydrocarbon feed source, there is still a need to identify processes that are suitable for handling heavy hydrocarbon feeds, such as Canadian bitumen. The present invention provides a low complexity, low severity, yet reliable operational procedure to separate and convert Canadian bitumen to produce a pipelineable product without the need for external diluent. The methods disclosed herein achieve this result by performing a lower complexity separation than typically used, while minimizing the conversion steps typically seen in producing refinery-type streams (e.g. minimizing the conversion steps decrease the complexity with a corresponding decrease in cost). In this way, much of the virgin portion of the feed bitumen can be used in the final product blend.
Current processes used in industry include combinations of diluent recovery (DRU)+vacuum distillation (VDU)+delayed coking+hydrotreating and/or DRU+VDU+heavy oil stripper+residue hydrocracking+hydrotreating and/or some combination of the first two. These processes produce a synthetic crude oil with API's above 30 which requires more processing than what is required to be sent in pipelines. The process according to an embodiment of the present invention yields a 19-21 API product (which meets pipeline specification) from a less complex process.